ISO-8062-1994.pdf
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1、INTERNATIONAL STANDARD IS0 8062 Second edition 1994-04-01 Castings - System of dimensional tolerances and machining allowances Pikes moukes - Syst b) machining requirements; c) method of casting; d) the number of castings to be manufactured; e) the casting equipment involved; f) any special requirem
2、ents, for instance, datum target systems, individ- ual dimensional tolerances, geometrical tolerances, fillet radii toler- ances and individual machining allowances; g) whether any other standard is more appropriate for the casting. NOTE 1 Further investigation on metallic permanent moulds (gravity-
3、 and low- pressure), pressure die castings and investment castings should be carried out. Because the dimensional accuracy of a casting is related to production factors, tolerance grades which can be achieved for various methods and metals are described in annex A for a) long series and mass product
4、ion, where development, adjustment and maintenance of casting equipment make it possible to achieve close tolerances; b) short series and single production. Information on typical required machining allowance grades is given in annex B. . III Copyright International Organization for Standardization
5、Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 07:19:54 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD * IS0 IS0 8062:1994(E) Castings - System of dimensional tolerances and machining
6、allowances 1 Scope This International Standard specifies a system of tol- erance grades and required machining allowance grades for the dimensions of castings. It is applicable to the dimensions of cast metals and their alloys produced by various casting manufacturing processes but see also Introduc
7、tion g) and dause 51. This International Standard applies both to general tolerances and/or required machining allowances given on a drawing and to individual tolerances and/or required machining allowances which are shown immediately following a specific dimension (see clause 11). The system specif
8、ied applies when the foundry pro- vides the pattern or die equipment or accepts re- sponsibility for proving it. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation
9、, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most re- cent editions of the standards indicated below. Members of IEC and IS0 maintain registers
10、of cur- rently valid International Standards. IS0 286-l :1988, IS0 system of limits and fits - Part 1: Bases of tolerances, deviations and fits. IS0 130211992, Technical drawings - Method of in- dicating surface texture. 3 Definitions For the purposes of this International Standard, the following de
11、finitions apply. 3.1 basic dimension: Dimension of a raw casting before machining (see figure 11, the necessary ma- chining allowance being included (see figure 2). Raw casting basic dimension 1 1 -.-.-.-.-.-.-.- .- - Raw casting b for example, if there is a general tolerance on a drawing of CTlO, t
12、he tolerance on wall thicknesses shall be CT1 1. 8 Tapered features Where a design requires a tapered feature (e.g. fea- ture with a draft angle), the tolerance shall be applied symmetrically along the surface (see figure4). Interpretation Basic dimension Basic dimension - =L CT/2 CT/2 a) Taper - b)
13、 Taper l I I CT/2 _ CT/2 c) Figure 4 - Tolerance zone on tapered features 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 07:19:54 MDTNo reproduction or networking permitted wi
14、thout license from IHS -,-,- IS0 8062:1994(E) Q IS0 The drawing shall specify generally whether the taper shall be added to, subtracted from or averaged to the material, e.g. taper +, figure4a) taper -, figure4 b) taper 5, figure4c) Tapers for particular surfaces arranged differently from the genera
15、l arrangement of taper of the drawing shall be indicated individually at the surface, e.g. d + . For dimensions to be machined, “taper +” shall be applied, irrespective of the general drawing specifica- tion for taper, in order that the finished dimensions can be achievable. 9 Position of tolerance
16、zone The tolerance zone, unless otherwise stated, shall be symmetrically disposed with respect to a basic di- mension, i.e. with one half on the positive side and one hatf on the negative side (see figure2). When agreed between manufacturer and purchaser for specific reasons, the tolerance zone may
17、be asymmetric. In such a case the tolerance shall be stated individually, following the basic dimension. 10 Required machining allowances, RMA 10.1 General Unless otherwise specified, the required machining allowance is valid for the entire raw casting, i.e. only one value is specified for all surfa
18、ces to be machined, and this shall be selected from the appropriate di- mension range according to the largest overall di- mension of the finished casting after final machining (see figure 9). The maximum dimension of a feature, as cast, shall not exceed the finished dimension plus the required mach
19、ining allowance plus the total casting tolerance (see figure 2 and figures 5 to 8). When applicable, the taper shall be considered additionally, as shown in figure 4. R=F+ZRMA+CT/2 CT/2 CT/2 R = Raw casting basic dimension F = Dimension after final machining RMA = Required machining allowance CT = C
20、asting tolerance Figure 5 - External machining of boss 4 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 07:19:54 MDTNo reproduction or networking permitted without license from
21、IHS -,-,- IS0 8062:1994(E) R=F-2RMA-CT/2 Figure 6 - Internal machining R=F (= F - RMA + RMA - CT/4 + CT/b) Figure 7 - Machining of step dimension / /: I- CT R = F + RMA + CT/2 I -I Figure 8 - Machining on one side of feature 5 Copyright International Organization for Standardization Provided by IHS
22、under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/20/2007 07:19:54 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 8062:1994(E) 0 IS0 II II Largest overall dimension Figure 9 - Largest overall dimension of the casting after final m
23、achining 10.2 Grades of required machining allowance There are 10 grades of required machining allowance, designated A to K (see table 2). NOTE 2 Grades recommended for particular alloys and manufacturing methods are shown in table B.l for informa- tion only. 10.3 Surfaces pre-machined by the foundr
24、y Any surfaces to be pre-machined by the foundry and the necessary machining allowances for the final ma- chining shall be stipulated on the drawing by the cus- tomer in accordance with IS0 1302. The required machining allowances necessary for the achievement of the pre-machined condition shall be t
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